Inkjet printhead nozzle with ribbed wall actuator

ABSTRACT

An ink jet printhead nozzle arrangement having an ink chamber formed in a wafer substrate and one wall of said chamber having at least one flexible portion. The ink ejection port is formed substantially centrally on the wall with a rim surrounding it. The wall is adapted to move independently of said rim. Rib elements are located on the outer surface of the wall to restrict the wall movement such that upon actuation of the at least one flexible portion of the wall, the wall is forced to move into said ink chamber, forcing ink therein out through the said ejection port.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 09/854,703 filed May 14, 2001, now abandoned, which is acontinuation of U.S. application Ser. No. 09/112,806 filed on Jul. 10,1998, now U.S. Pat. No. 6,247,790. The disclosure of U.S. Pat. No.6,247,790 is specifically incorporated herein by reference.

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication Ser. Nos. (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

US PATENT/PATENT APPLICATION (CLAIMING RIGHT OF CROSS-REFERENCEDPRIORITY FROM AUSTRALIAN AUSTRALIAN PROVISIONAL PATENT PROVISIONALAPPLICATION NO. APPLICATION) DOCKET NO. PO7991 6,750,901 ART01 PO85056,476,863 ART02 PO7988 09/113,073 ART03 PO9395 6,322,181 ART04 PO80176,597,817 ART06 PO8014 6,227,648 ART07 PO8025 6,727,948 ART08 PO80326,690,419 ART09 PO7999 6,727,951 ART10 PO7998 09/112,742 ART11 PO803109/112,741 ART12 PO8030 6,196,541 ART13 PO7997 6,195,150 ART15 PO79796,362,868 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO79826,431,669 ART19 PO7989 6,362,869 ART20 PO8019 6,472,052 ART21 PO79806,356,715 ART22 PO8018 09/112,777 ART24 PO7938 6,636,216 ART25 PO80166,366,693 ART26 PO8024 6,329,990 ART27 PO7940 09/113,072 ART28 PO79396,459,495 ART29 PO8501 6,137,500 ART30 PO8500 6,690,416 ART31 PO798709/113,071 ART32 PO8022 6,398,328 ART33 PO8497 09/113,090 ART34 PO80206,431,704 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO80006,415,054 ART43 PO7977 09/112,782 ART44 PO7934 6,665,454 ART45 PO799009/113,059 ART46 PO8499 6,486,886 ART47 PO8502 6,381,361 ART48 PO79816,317,192 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO80266,646,757 ART53 PO8027 09/112,759 ART54 PO8028 6,624,848 ART56 PO93946,357,135 ART57 PO9396 09/113,107 ART58 PO9397 6,271,931 ART59 PO93986,353,772 ART60 PO9399 6,106,147 ART61 PO9400 6,665,008 ART62 PO94016,304,291 ART63 PO9402 09/112,788 ART64 PO9403 6,305,770 ART65 PO94056,289,262 ART66 PP0959 6,315,200 ART68 PP1397 6,217,165 ART69 PP237009/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 6,350,023 Fluid01 PO80056,318849 Fluid02 PO9404 09/113,101 Fluid03 PO8066 6,227,652 IJ01 PO80726,213,588 IJ02 PO8040 6,213,589 IJ03 PO8071 6,231,163 IJ04 PO80476,247,795 IJ05 PO8035 6,394,581 IJ06 PO8044 6,244,691 IJ07 PO80636,257,704 IJ08 PO8057 6,416,168 IJ09 PO8056 6,220,694 IJ10 PO80696,257,705 IJ11 PO8049 6,247,794 IJ12 PO8036 6,234,610 IJ13 PO80486,247,793 IJ14 PO8070 6,264,306 IJ15 PO8067 6,241,342 IJ16 PO80016,247,792 IJ17 PO8038 6,264,307 IJ18 PO8033 6,254,220 IJ19 PO80026,234,611 IJ20 PO8068 6,302,528 IJ21 PO8062 6,283,582 IJ22 PO80346,239,821 IJ23 PO8039 6,338,547 IJ24 PO8041 6,247,796 IJ25 PO80046,557,977 IJ26 PO8037 6,390,603 IJ27 PO8043 6,362,843 IJ28 PO80426,293,653 IJ29 PO8064 6,312,107 IJ30 PO9389 6,227,653 IJ31 PO93916,234,609 IJ32 PP0888 6,238,040 IJ33 PP0891 6,188,415 IJ34 PP08906,227,654 IJ35 PP0873 6,209,989 IJ36 PP0993 6,247,791 IJ37 PP08906,336,710 IJ38 PP1398 6,217,153 IJ39 PP2592 6,416,167 IJ40 PP25936,243,113 IJ41 PP3991 6,283,581 IJ42 PP3987 6,247,790 IJ43 PP39856,260,953 IJ44 PP3983 6,267,469 IJ45 PO7935 6,224,780 IJM01 PO79366,235,212 IJM02 PO7937 6,280,643 IJM03 PO8061 6,284,147 IJM04 PO80546,214,244 IJM05 PO8065 6,071,750 IJM06 PO8055 6,267,905 IJM07 PO80536,251,298 IJM08 PO8078 6,258,285 IJM09 PO7933 6,225,138 IJM10 PO79506,241,904 IJM11 PO7949 6,299,786 IJM12 PO8060 09/113,124 IJM13 PO80596,231,773 IJM14 PO8073 6,190,931 IJM15 PO8076 6,248,249 IJM16 PO80756,290,862 IJM17 PO8079 6,241,906 IJM18 PO8050 6,565,762 IJM19 PO80526,241,905 IJM20 PO7948 6,451,216 IJM21 PO7951 6,231,772 IJM22 PO80746,274,056 IJM23 PO7941 6,290,861 IJM24 PO8077 6,248,248 IJM25 PO80586,306,671 IJM26 PO8051 6,331,258 IJM27 PO8045 6,111,754 IJM28 PO79526,294,101 IJM29 PO8046 6,416,679 IJM30 PO9390 6,264,849 IJM31 PO93926,254,793 IJM32 PP0889 6,235,211 IJM35 PP0887 6,491,833 IJM36 PP08826,264,850 IJM37 PP0874 6,258,284 IJM38 PP1396 6,312,615 IJM39 PP39896,228,668 IJM40 PP2591 6,180,427 IJM41 PP3990 6,171,875 IJM42 PP39866,267,904 IJM43 PP3984 6,245,247 IJM44 PP3982 6,315,914 IJM45 PP08956,231,148 IR01 PP0870 09/113,106 IR02 PP0869 6,293,658 IR04 PP08876,614,560 IR05 PP0885 6,238,033 IR06 PP0884 6,312,070 IR10 PP08866,238,111 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP08776,378,970 IR16 PP0878 6,196,739 IR17 PP0879 09/112,774 IR18 PP08836,270,182 IR19 PP0880 6,152,619 IR20 PP0881 09/113,092 IR21 PO80066,087,638 MEMS02 PO8007 6,340,222 MEMS03 PO8008 09/113,062 MEMS04 PO80106,041,600 MEMS05 PO8011 6,299,300 MEMS06 PO7947 6,067,797 MEMS07 PO79446,286,935 MEMS09 PO7946 6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP087509/113,078 MEMS12 PP0894 6,382,769 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the field of inkjet printing and, inparticular, discloses an inverted radial back-curling thermoelastic inkjet printing mechanism.

BACKGROUND OF THE INVENTION

Many different types of printing mechanisms have been invented, a largenumber of which are presently in use. The known forms of printers have avariety of methods for marking the print media with a relevant markingmedia. Commonly used forms of printing include offset printing, laserprinting and copying devices, dot matrix type impact printers, thermalpaper printers, film recorders, thermal wax printers, dye sublimationprinters and ink jet printers both of the drop on demand and continuousflow type. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles, has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques of inkjet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different forms. Theutilization of a continuous stream of ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including a step wherein the ink jet streamis modulated by a high frequency electro-static field so as to causedrop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al).

Piezoelectric inkjet printers are also one form of commonly utilizedinkjet printing device. Piezoelectric systems are disclosed by Kyser et.al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode ofoperation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses asqueeze mode form of operation of a piezoelectric crystal, Stemme inU.S. Pat. No. 3,747,120 (1972) which discloses a bend mode ofpiezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 whichdiscloses a piezoelectric push mode actuation of the ink jet stream andFischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode typeof piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. No. 4,490,728. Both the aforementioned references disclose ink jetprinting techniques which rely on the activation of an electrothermalactuator which results in the creation of a bubble in a constrictedspace, such as a nozzle, which thereby causes the ejection of ink froman aperture connected to the confined space onto a relevant print media.Printing devices utilizing the electro-thermal actuator are manufacturedby manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction and operation, durability andconsumables.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there isprovided a nozzle arrangement for an ink jet printhead, the arrangementcomprising: a nozzle chamber defined in a wafer substrate for thestorage of ink to be ejected; an ink ejection port having a rim formedon one wall of the chamber; and a series of actuators attached to thewafer substrate, and forming a portion of the wall of the nozzle chamberadjacent the rim, the actuator paddles further being actuated in unisonso as to eject ink from the nozzle chamber via the ink ejection nozzle.

The actuators can include a surface which bends inwards away from thecentre of the nozzle chamber upon actuation. The actuators arepreferably actuated by means of a thermal actuator device. The thermalactuator device may comprise a conductive resistive heating elementencased within a material having a high coefficient of thermalexpansion. The element can be serpentine to allow for substantiallyunhindered expansion of the material. The actuators are preferablyarranged radially around the nozzle rim.

The actuators can form a membrane between the nozzle chamber and anexternal atmosphere of the arrangement and the actuators bend away fromthe external atmosphere to cause an increase in pressure within thenozzle chamber thereby initiating a consequential ejection of ink fromthe nozzle chamber. The actuators can bend away from a central axis ofthe nozzle chamber.

The nozzle arrangement can be formed on the wafer substrate utilizingmicro-electro mechanical techniques and further can comprise an inksupply channel in communication with the nozzle chamber. The ink supplychannel may be etched through the wafer. The nozzle arrangement mayinclude a series of struts which support the nozzle rim.

The arrangement can be formed adjacent to neighbouring arrangements soas to form a pagewidth printhead.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIGS. 1-3 are schematic sectional views illustrating the operationalprinciples of the preferred embodiment;

FIG. 4(a) and FIG. 4(b) are again schematic sections illustrating theoperational principles of the thermal actuator device;

FIG. 5 is a side perspective view, partly in section, of a single nozzlearrangement constructed in accordance with the preferred embodiments;

FIGS. 6-13 are side perspective views, partly in section, illustratingthe manufacturing steps of the preferred embodiments;

FIG. 14 illustrates an array of ink jet nozzles formed in accordancewith the manufacturing procedures of the preferred embodiment;

FIG. 15 provides a legend of the materials indicated in FIGS. 16 to 23;and

FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing stepsin one form of construction of a nozzle arrangement in accordance withthe invention.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, ink is ejected out of a nozzle chamber viaan ink ejection port using a series of radially positioned thermalactuator devices that are arranged about the ink ejection port and areactivated to pressurize the ink within the nozzle chamber therebycausing the ejection of ink through the ejection port.

Turning now to FIGS. 1, 2 and 3, there is illustrated the basicoperational principles of the preferred embodiment. FIG. 1 illustrates asingle nozzle arrangement 1 in its quiescent state. The arrangement 1includes a nozzle chamber 2 which is normally filled with ink so as toform a meniscus 3 in an ink ejection port 4. The nozzle chamber 2 isformed within a wafer 5. The nozzle chamber 2 is supplied with ink viaan ink supply channel 6 which is etched through the wafer 5 with ahighly isotropic plasma etching system. A suitable etcher can be theAdvance Silicon Etch (ASE) system available from Surface TechnologySystems of the United Kingdom.

A top of the nozzle arrangement 1 includes a series of radiallypositioned actuators 8, 9. These actuators comprise apolytetrafluoroethylene (PTFE) layer and an internal serpentine coppercore 17. Upon heating of the copper core 17, the surrounding PTFEexpands rapidly resulting in a generally downward movement of theactuators 8, 9. Hence, when it is desired to eject ink from the inkejection port 4, a current is passed through the actuators 8, 9 whichresults in them bending generally downwards as illustrated in FIG. 2.The downward bending movement of the actuators 8, 9 results in asubstantial increase in pressure within the nozzle chamber 2. Theincrease in pressure in the nozzle chamber 2 results in an expansion ofthe meniscus 3 as illustrated in FIG. 2.

The actuators 8, 9 are activated only briefly and subsequentlydeactivated. Consequently, the situation is as illustrated in FIG. 3with the actuators 8, 9 returning to their original positions. Thisresults in a general inflow of ink back into the nozzle chamber 2 and anecking and breaking of the meniscus 3 resulting in the ejection of adrop 12. The necking and breaking of the meniscus 3 is a consequence ofthe forward momentum of the ink associated with drop 12 and the backwardpressure experienced as a result of the return of the actuators 8, 9 totheir original positions. The return of the actuators 8,9 also resultsin a general inflow of ink from the channel 6 as a result of surfacetension effects and, eventually, the state returns to the quiescentposition as illustrated in FIG. 1.

FIGS. 4(a) and 4(b) illustrate the principle of operation of the thermalactuator. The thermal actuator is preferably constructed from a material14 having a high coefficient of thermal expansion. Embedded within thematerial 14 are a series of heater elements 15 which can be a series ofconductive elements designed to carry a current. The conductive elements15 are heated by passing a current through the elements 15 with theheating resulting in a general increase in temperature in the areaaround the heating elements 15. The position of the elements 15 is suchthat uneven heating of the material 14 occurs. The uneven increase intemperature causes a corresponding uneven expansion of the material 14.Hence, as illustrated in FIG. 4(b), the PTFE is bent generally in thedirection shown.

In FIG. 5, there is illustrated a side perspective view of oneembodiment of a nozzle arrangement constructed in accordance with theprinciples previously outlined. The nozzle chamber 2 is formed with anisotropic surface etch of the wafer 5. The wafer 5 can include a CMOSlayer including all the required power and drive circuits. Further, theactuators 8, 9 each have a leaf or petal formation which extends towardsa nozzle rim 28 defining the ejection port 4. The normally inner end ofeach leaf or petal formation is displaceable with respect to the nozzlerim 28. Each activator 8, 9 has an internal copper core 17 defining theelement 15. The core 17 winds in a serpentine manner to provide forsubstantially unhindered expansion of the actuators 8, 9. The operationof the actuators 8, 9 is as illustrated in FIG. 4(a) and FIG. 4(b) suchthat, upon activation, the actuators 8 bend as previously describedresulting in a displacement of each petal formation away from the nozzlerim 28 and into the nozzle chamber 2. The ink supply channel 6 can becreated via a deep silicon back edge of the wafer 5 utilizing a plasmaetcher or the like. The copper or aluminium core 17 can provide acomplete circuit. A central arm 18 which can include both metal and PTFEportions provides the main structural support for the actuators 8, 9.

Turning now to FIG. 6 to FIG. 13, one form of manufacture of the nozzlearrangement 1 in accordance with the principles of the preferredembodiment is shown. The nozzle arrangement 1 is preferably manufacturedusing microelectromechanical (MEMS) techniques and can include thefollowing construction techniques:

As shown initially in FIG. 6, the initial processing starting materialis a standard semi-conductor wafer 20 having a complete CMOS level 21 toa first level of metal. The first level of metal includes portions 22which are utilized for providing power to the thermal actuators 8, 9.

The first step, as illustrated in FIG. 7, is to etch a nozzle regiondown to the silicon wafer 20 utilizing an appropriate mask.

Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene(PTFE) is deposited and etched so as to define vias 24 forinterconnecting multiple levels.

Next, as illustrated in FIG. 9, the second level metal layer isdeposited, masked and etched to define a heater structure 25. The heaterstructure 25 includes via 26 interconnected with a lower aluminiumlayer.

Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE isdeposited and etched to the depth of 1 μm utilizing a nozzle rim mask todefine the nozzle rim 28 in addition to ink flow guide rails 29 whichgenerally restrain any wicking along the surface of the PTFE layer. Theguide rails 29 surround small thin slots and, as such, surface tensioneffects are a lot higher around these slots which in turn results inminimal outflow of ink during operation.

Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzleand actuator mask to define a port portion 30 and slots 31 and 32.

Next, as illustrated in FIG. 12, the wafer is crystallographicallyetched on a <111> plane utilizing a standard crystallographic etchantsuch as KOH. The etching forms a chamber 33, directly below the portportion 30.

In FIG. 13, the ink supply channel 34 can be etched from the back of thewafer utilizing a highly anisotropic etcher such as the STS etcher fromSilicon Technology Systems of United Kingdom. An array of ink jetnozzles can be formed simultaneously with a portion of an array 36 beingillustrated in FIG. 14. A portion of the printhead is formedsimultaneously and diced by the STS etching process. The array 36 shownprovides for four column printing with each separate column attached toa different colour ink supply channel being supplied from the back ofthe wafer. Bond pads 37 provide for electrical control of the ejectionmechanism.

In this manner, large pagewidth printheads can be fabricated so as toprovide for a drop-on-demand ink ejection mechanism.

One form of detailed manufacturing process which can be used tofabricate monolithic inkjet printheads operating in accordance with theprinciples taught by the present embodiment can proceed utilizing thefollowing steps:

1. Using a double-sided polished wafer 60, complete a 0.5 micron, onepoly, 2 metal CMOS process 61. This step shown in FIG. 16. For clarity,these diagrams may not be to scale, and may not represent a crosssection though any single plane of the nozzle. FIG. 15 is a key torepresentations of various materials in these manufacturing diagrams,and those of other cross referenced ink jet configurations.

2. Etch the CMOS oxide layers down to silicon or second level metalusing Mask 1. This mask defines the nozzle cavity and the edge of thechips. This step is shown in FIG. 16.

3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treatthe surface of this polymer for PTFE adherence.

4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 62.

5. Etch the PTFE and CMOS oxide layers to second level metal using Mask2. This mask defines the contact vias for the heater electrodes. Thisstep is shown in FIG. 17.

6. Deposit and pattern 0.5 microns of gold 63 using a lift-off processusing Mask 3. This mask defines the heater pattern. This step is shownin FIG. 18.

7. Deposit 1.5 microns of PTFE 64.

8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim65 and the rim at the edge 66 of the nozzle chamber. This step is shownin FIG. 19.

9. Etch both layers of PTFE and the thin hydrophilic layer down tosilicon using Mask 5. This mask defines a gap 67 at inner edges of theactuators, and the edge of the chips. It also forms the mask for asubsequent crystallographic etch. This step is shown in FIG. 20.

10. Crystallographically etch the exposed silicon using KOH. This etchstops on <111> crystallographic planes 68, forming an inverted squarepyramid with sidewall angles of 54.74 degrees. This step is shown inFIG. 21.

11. Back-etch through the silicon wafer (with, for example, an ASEAdvanced Silicon Etcher from Surface Technology Systems) using Mask 6.This mask defines the ink inlets 69 which are etched through the wafer.The wafer is also diced by this etch. This step is shown in FIG. 22.

12. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets 69 at the back of the wafer.

13. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

14. Fill the completed print heads with ink 70 and test them. A fillednozzle is shown in FIG. 23.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic“minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric inkjet is size and cost.Piezoelectric crystals have a very small deflection at reasonable drivevoltages, and therefore require a large area for each nozzle. Also, eachpiezoelectric actuator must be connected to its drive circuit on aseparate substrate. This is not a significant problem at the currentlimit of around 300 nozzles per printhead, but is a major impediment tothe fabrication of pagewidth printheads with 19,200 nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

-   -   photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table below under the heading CrossReferences to Related Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain inkjettypes have been investigated in detail. These are designated IJ01 toIJ45 above which matches the docket numbers in the table under theheading Cross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal Largeforce High power Canon Bubblejet bubble heater heats the ink togenerated Ink carrier limited to 1979 Endo et al GB above boiling point,Simple construction water patent 2,007,162 transferring significant Nomoving parts Low efficiency Xerox heater-in-pit heat to the aqueous Fastoperation High temperatures 1990 Hawkins et al ink. A bubble Small chiparea required USP 4,899,181 nucleates and quickly required for actuatorHigh mechanical Hewlett-Packard TIJ forms, expelling the stress 1982Vaught et al ink. Unusual materials USP 4,490,728 The efficiency of therequired process is low, with Large drive typically less thantransistors 0.05% of the electrical Cavitation causes energy beingactuator failure transformed into Kogation reduces kinetic energy of thebubble formation drop. Large print heads are difficult to fabricatePiezoelectric A piezoelectric crystal Low power Very large area Kyser etal USP such as lead consumption required for actuator 3,946,398lanthanum zirconate Many ink types can Difficult to integrate Zoltan USP(PZT) is electrically be used with electronics 3,683,212 activated, andeither Fast operation High voltage drive 1973 Stemme USP expands,shears, or High efficiency transistors required 3,747,120 bends to applyFull pagewidth print Epson Stylus pressure to the ink, heads impracticalTektronix ejecting drops. due to actuator size IJ04 Requires electricalpoling in high field strengths during manufacture Electrostrictive Anelectric field is Low power Low maximum Seiko Epson, Usui used toactivate consumption strain (approx. et all JP 253401/96electrostriction in Many ink types can 0.01%) IJ04 relaxor materialssuch be used Large area required as lead lanthanum Low thermal foractuator due to zirconate titanate expansion low strain (PLZT) or leadElectric field Response speed is magnesium niobate strength requiredmarginal (˜10 (PMN). (approx. 3.5 V/μm) μs) can High voltage drive begenerated transistors required without difficulty Full pagewidth printDoes not require heads impractical electrical poling due to actuatorsize Ferroelectric An electric field is Low power Difficult to integrateIJ04 used to induce a phase consumption with electronics transitionbetween the Many ink types can Unusual materials antiferroelectric (AFE)be used such as PLZSnT are and ferroelectric (FE) Fast operation (<1required phase. Perovskite μs) Actuators require a materials such as tinRelatively high large area modified lead longitudinal strain lanthanumzirconate High efficiency titanate (PLZSnT) Electric field exhibit largestrains of strength of around 3 V/μm up to 1% associated can be with theAFE to FE readily provided phase transition. Electrostatic Conductiveplates are Low power Difficult to operate IJ02, IJ04 plates separated bya consumption electrostatic devices compressible or fluid Many ink typescan in an aqueous dielectric (usually air). be used environment Uponapplication of a Fast operation The electrostatic voltage, the platesactuator will attract each other and normally need to be displace ink,causing separated from the drop ejection. The ink conductive plates mayVery large area be in a comb or required to achieve honeycomb structure,high forces or stacked to increase High voltage drive the surface areaand transistors may be therefore the force. required Full pagewidthprint heads are not competitive due to actuator size Electrostatic Astrong electric field Low current High voltage 1989 Saito et al, pull isapplied to the ink, consumption required USP 4,799,068 on ink whereuponLow temperature May be damaged by 1989 Miura et al, electrostaticattraction sparks due to air USP 4,810,954 accelerates the ink breakdownTone-jet towards the print Required field medium. strength increases asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent An electromagnet Low powerComplex fabrication IJ07, IJ10 magnet directly attracts a consumptionPermanent magnetic electromagnetic permanent magnet, Many ink types canmaterial such as displacing ink and be used Neodymium Iron causing dropejection. Fast operation Boron (NdFeB) Rare earth magnets Highefficiency required. with a field strength Easy extension from Highlocal currents around 1 Tesla can be single nozzles to required used.Examples are: pagewidth print Copper metalization Samarium Cobalt headsshould be used for (SaCo) and magnetic long materials in theelectromigration neodymium iron boron lifetime and low family (NdFeB,resistivity NdDyFeBNb, Pigmented inks are NdDyFeB, etc) usuallyinfeasible Operating temperature limited to the Curie temperature(around 540K) Soft A solenoid induced a Low power Complex fabricationIJ01, IJ05, IJ08, magnetic magnetic field in a soft consumptionMaterials not IJ10, IJ12, IJ14, core electromagnetic magnetic core oryoke Many ink types can usually present in a IJ15, IJ17 fabricated froma be used CMOS fab such as ferrous material such Fast operation NiFe,CoNiFe, or as electroplated iron High efficiency CoFe are requiredalloys such as CoNiFe Easy extension from High local currents [1], CoFe,or NiFe single nozzles to required alloys. Typically, the pagewidthprint Copper metalization soft magnetic material heads should be usedfor is in two parts, which long are normally held electromigration apartby a spring. lifetime and low When the solenoid is resistivity actuated,the two parts Electroplating is attract, displacing the required ink.High saturation flux density is required (2.0-2.1 T is achievable withCoNiFe [1]) Lorenz The Lorenz force Low power Force acts as a IJ06,IJ11, IJ13, force acting on a current consumption twisting motion IJ16carrying wire in a Many ink types can Typically, only a magnetic fieldis be used quarter of the utilized. Fast operation solenoid length Thisallows the High efficiency provides force in a magnetic field to be Easyextension from useful direction supplied externally to single nozzles toHigh local currents the print head, for pagewidth print required examplewith rare heads Copper metalization earth permanent should be used formagnets. long Only the current electromigration carrying wire need belifetime and low fabricated on the print- resistivity head, simplifyingPigmented inks are materials usually infeasible requirements.Magnetostriction The actuator uses the Many ink types can Force acts asa Fischenbeck, USP giant magnetostrictive be used twisting motion4,032,929 effect of materials Fast operation Unusual materials IJ25 suchas Terfenol-D (an Easy extension from such as Terfenol-D alloy ofterbium, single nozzles to are required dysprosium and iron pagewidthprint High local currents developed at the Naval heads required OrdnanceLaboratory, High force is Copper metalization hence Ter-Fe-NOL).available should be used for For best efficiency, the long actuatorshould be pre- electromigration stressed to approx. 8 MPa. lifetime andlow resistivity Pre-stressing may be required Surface Ink under positiveLow power Requires Silverbrook, EP tension pressure is held in aconsumption supplementary force 0771 658 A2 and reduction nozzle bysurface Simple construction to effect drop related patent tension. Thesurface No unusual separation applications tension of the ink ismaterials required in Requires special ink reduced below the fabricationsurfactants bubble threshold, High efficiency Speed may be causing theink to Easy extension from limited by surfactant egress from the singlenozzles to properties nozzle. pagewidth print heads Viscosity The inkviscosity is Simple construction Requires Silverbrook, EP reductionlocally reduced to No unusual supplementary force 0771 658 A2 and selectwhich drops are materials required in to effect drop related patent tobe ejected. A fabrication separation applications viscosity reductioncan Easy extension from Requires special ink be achieved single nozzlesto viscosity properties electrothermally with pagewidth print High speedis most inks, but special heads difficult to achieve inks can beengineered Requires oscillating for a 100:1 viscosity ink pressurereduction. A high temperature difference (typically 80 degrees) isrequired Acoustic An acoustic wave is Can operate without Complex drive1993 Hadimioglu et generated and a nozzle plate circuitry al, EUP550,192 focussed upon the Complex fabrication 1993 Elrod et al, dropejection region. Low efficiency EUP 572,220 Poor control of dropposition Poor control of drop volume Thermoelastic An actuator which Lowpower Efficient aqueous IJ03, IJ09, IJ17, bend relies upon differentialconsumption operation requires a IJ18, IJ19, IJ20, actuator thermalexpansion Many ink types can thermal insulator on IJ21, IJ22, IJ23, uponJoule heating is be used the hot side IJ24, IJ27, IJ28, used. Simpleplanar Corrosion IJ29, IJ30, IJ31, fabrication prevention can be IJ32,IJ33, IJ34, Small chip area difficult IJ35, IJ36, IJ37, required foreach Pigmented inks may IJ38, IJ39, IJ40, actuator be infeasible, asIJ41 Fast operation pigment particles High efficiency may jam the bendCMOS compatible actuator voltages and currents Standard MEMS processescan be used Easy extension from single nozzles to pagewidth print headsHigh CTE A material with a very High force can be Requires special IJ09,IJ17, IJ18, thermoelastic high coefficient of generated material (e.g.PTFE) IJ20, IJ21, IJ22, actuator thermal expansion Three methods ofRequires a PTFE IJ23, IJ24, IJ27, (CTE) such as PTFE deposition aredeposition process, IJ28, IJ29, IJ30, polytetrafluoroethylene underdevelopment: which is not yet IJ31, IJ42, IJ43, (PTFE) is used. Aschemical vapor standard in ULSI IJ44 high CTE materials deposition(CVD), fabs are usually non- spin coating, and PTFE depositionconductive, a heater evaporation cannot be followed fabricated from aPTFE is a candidate with high conductive material is for low dielectrictemperature (above incorporated. A 50 constant insulation 350° C.)processing μm long PTFE in ULSI Pigmented inks may bend actuator withVery low power be infeasible, as polysilicon heater and consumptionpigment particles 15 mW power input Many ink types can may jam the bendcan provide 180 be used actuator μN force Simple planar and 10 μmfabrication deflection. Actuator Small chip area motions include:required for each Bend actuator Push Fast operation Buckle Highefficiency Rotate CMOS compatible voltages and currents Easy extensionfrom single nozzles to pagewidth print heads Conductive A polymer with ahigh High force can be Requires special IJ24 polymer coefficient ofthermal generated materials thermoelastic expansion (such as Very lowpower development (High actuator PTFE) is doped with consumption CTEconductive conducting substances Many ink types can polymer) to increaseits be used Requires a PTFE conductivity to about 3 Simple planardeposition process, orders of magnitude fabrication which is not yetbelow that of copper. Small chip area standard in ULSI The conductingrequired for each fabs polymer expands actuator PTFE deposition whenresistively Fast operation cannot be followed heated. High efficiencywith high Examples of CMOS compatible temperature (above conductingdopants voltages and 350° C.) processing include: currents Evaporationand Carbon nanotubes Easy extension from CVD deposition Metal fiberssingle nozzles to techniques cannot Conductive polymers pagewidth printbe used such as doped heads Pigmented inks may polythiophene beinfeasible, as Carbon granules pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) is developed at the Naval available (more thanrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate limited between its weakresistance by heat removal martensitic state and Simple constructionRequires unusual its high stiffness Easy extension from materials (TiNi)austenic state. The single nozzles to The latent heat of shape of theactuator pagewidth print transformation must in its martensitic stateheads be provided is deformed relative to Low voltage High current theaustenic shape. operation operation The shape change Requires pre-causes ejection of a stressing to distort drop. the martensitic stateLinear Linear magnetic Linear Magnetic Requires unusual IJ12 Magneticactuators include the actuators can be semiconductor Actuator LinearInduction constructed with materials such as Actuator (LIA), Linear highthrust, long soft magnetic alloys Permanent Magnet travel, and high(e.g. CoNiFe) Synchronous Actuator efficiency using Some varieties also(LPMSA), Linear planar require permanent Reluctance semiconductormagnetic materials Synchronous Actuator fabrication such as Neodymium(LRSA), Linear techniques iron boron (NdFeB) Switched Reluctance Longactuator travel Requires complex Actuator (LSRA), and is availablemulti-phase drive the Linear Stepper Medium force is circuitry Actuator(LSA). available High current Low voltage operation operation BASICOPERATION MODE Actuator This is the simplest Simple operation Droprepetition rate Thermal ink jet directly mode of operation: the Noexternal fields is usually limited to Piezoelectric ink jet pushes inkactuator directly required around 10 kHz. IJ01, IJ02, IJ03, suppliessufficient Satellite drops can However, this is not IJ04, IJ05, IJ06,kinetic energy to expel be avoided if drop fundamental to the IJ07,IJ09, IJ11, the drop. The drop velocity is less than method, but isIJ12, IJ14, IJ16, must have a sufficient 4 m/s related to the refillIJ20, IJ22, IJ23, velocity to overcome Can be efficient, method normallyIJ24, IJ25, IJ26, the surface tension. depending upon the used IJ27,IJ28, IJ29, actuator used All of the drop IJ30, IJ31, IJ32, kineticenergy must IJ33, IJ34, IJ35, be provided by the IJ36, IJ37, IJ38,actuator IJ39, IJ40, IJ41, Satellite drops IJ42, IJ43, IJ44 usually formif drop velocity is greater than 4.5 m/s Proximity The drops to be Verysimple print Requires close Silverbrook, EP printed are selected by headfabrication can proximity between 0771 658 A2 and some manner (e.g. beused the print head and related patent thermally induced The dropselection the print media or applications surface tension means does notneed transfer roller reduction of to provide the May require twopressurized ink). energy required to print heads printing Selected dropsare separate the drop alternate rows of the separated from the ink fromthe nozzle image in the nozzle by Monolithic color contact with theprint print heads are medium or a transfer difficult roller.Electrostatic The drops to be Very simple print Requires very highSilverbrook, EP pull printed are selected by head fabrication canelectrostatic field 0771 658 A2 and on ink some manner (e.g. be usedElectrostatic field related patent thermally induced The drop selectionfor small nozzle applications surface tension means does not need sizesis above air Tone-Jet reduction of to provide the breakdown pressurizedink). energy required to Electrostatic field Selected drops are separatethe drop may attract dust separated from the ink from the nozzle in thenozzle by a strong electric field. Magnetic The drops to be Very simpleprint Requires magnetic Silverbrook, EP pull on ink printed are selectedby head fabrication can ink 0771 658 A2 and some manner (e.g. be usedInk colors other than related patent thermally induced The dropselection black are difficult applications surface tension means doesnot need Requires very high reduction of to provide the magnetic fieldspressurized ink). energy required to Selected drops are separate thedrop separated from the ink from the nozzle in the nozzle by a strongmagnetic field acting on the magnetic ink. Shutter The actuator moves aHigh speed (>50 kHz) Moving parts are IJ13, IJ17, IJ21 shutter to blockink operation can required flow to the nozzle. The be achieved due toRequires ink ink pressure is pulsed reduced refill time pressuremodulator at a multiple of the Drop timing can be Friction and wear dropejection very accurate must be considered frequency. The actuator energyStiction is possible can be very low Shuttered The actuator moves aActuators with Moving parts are IJ08, IJ15, IJ18, grill shutter to blockink small travel can be required IJ19 flow through a grill to usedRequires ink the nozzle. The shutter Actuators with pressure modulatormovement need only small force can be Friction and wear be equal to thewidth used must be considered of the grill holes. High speed (>50 kHz)Stiction is possible operation can be achieved Pulsed A pulsed magneticExtremely low Requires an external IJ10 magnetic field attracts an ‘inkenergy operation is pulsed magnetic pull on ink pusher’ at the droppossible field pusher ejection frequency. An No heat dissipationRequires special actuator controls a problems materials for both catch,which prevents the actuator and the the ink pusher from ink pushermoving when a drop is Complex not to be ejected. construction AUXILIARYMECHANISM (APPLIED TO ALL NOZZLES) None The actuator directly Simplicityof Drop ejection Most ink jets, fires the ink drop, and constructionenergy must be including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical size actuator IJ01, IJ02,IJ03, IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, oscillator related patentacoustic ejection energy. The allowing higher Ink pressure phaseapplications stimulation) actuator selects which operating speed andamplitude must IJ08, IJ13, IJ15, drops are to be fired The actuators maybe carefully IJ17, IJ18, IJ19, by selectively operate with muchcontrolled IJ21 blocking or enabling lower energy Acoustic reflectionsnozzles. The ink Acoustic lenses can in the ink chamber pressureoscillation be used to focus the must be designed may be achieved bysound on the for vibrating the print nozzles head, or preferably by anactuator in the ink supply. Media The print head is Low power Precisionassembly Silverbrook, EP proximity placed in close High accuracyrequired 0771 658 A2 and proximity to the print Simple print head Paperfibers may related patent medium. Selected construction cause problemsapplications drops protrude from Cannot print on the print head furtherrough substrates than unselected drops, and contact the print medium.The drop soaks into the medium fast enough to cause drop separation.Transfer Drops are printed to a High accuracy Bulky Silverbrook, EProller transfer roller instead Wide range of print Expensive 0771 658 A2and of straight to the print substrates can be Complex related patentmedium. A transfer used construction applications roller can also beused Ink can be dried on Tektronix hot melt for proximity drop thetransfer roller piezoelectric ink jet separation. Any of the IJ seriesElectrostatic An electric field is Low power Field strength Silverbrook,EP used to accelerate Simple print head required for 0771 658 A2 andselected drops towards construction separation of small related patentthe print medium. drops is near or applications above air Tone-Jetbreakdown Direct A magnetic field is Low power Requires magneticSilverbrook, EP magnetic used to accelerate Simple print head ink 0771658 A2 and field selected drops of construction Requires strong relatedpatent magnetic ink towards magnetic field applications the printmedium. Cross The print head is Does not require Requires external IJ06,IJ16 magnetic placed in a constant magnetic materials magnet fieldmagnetic field. The to be integrated in Current densities Lorenz forcein a the print head may be high, current carrying wire manufacturingresulting in is used to move the process electromigration actuator.problems Pulsed A pulsed magnetic Very low power Complex print head IJ10magnetic field is used to operation is possible construction fieldcyclically attract a Small print head Magnetic materials paddle, whichpushes size required in print on the ink. A small head actuator moves acatch, which selectively prevents the paddle from moving. ACTUATORAMPLIFICATION OR MODIFICATION METHOD None No actuator Operational Manyactuator Thermal Bubble Ink mechanical simplicity mechanisms have jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be taken IJ18, IJ19, IJ20, actuator The expansion may be thatthe materials do IJ21, IJ22, IJ23, thermal, piezoelectric, notdelaminate IJ24, IJ27, IJ29, magnetostrictive, or Residual bend IJ30,IJ31, IJ32, other mechanism. The resulting from high IJ33, IJ34, IJ35,bend actuator converts temperature or high IJ36, IJ37, IJ38, a highforce low travel stress during IJ39, IJ42, IJ43, actuator mechanism toformation IJ44 high travel, lower force mechanism. Transient A trilayerbend Very good High stresses are IJ40, IJ41 bend actuator where the twotemperature stability involved actuator outside layers are High speed,as a Care must be taken identical. This cancels new drop can be that thematerials do bend due to ambient fired before heat not delaminatetemperature and dissipates residual stress. The Cancels residualactuator only responds stress of formation to transient heating of oneside or the other. Reverse The actuator loads a Better coupling toFabrication IJ05, IJ11 spring spring. When the the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some piezoelectricstack actuators are stacked. Reduced drive fabrication ink jets This canbe voltage complexity IJ04 appropriate where Increased possibilityactuators require high of short circuits due electric field strength, topinholes such as electrostatic and piezoelectric actuators. MultipleMultiple smaller Increases the force Actuator forces may IJ12, IJ13,IJ18, actuators actuators are used available from an not add linearly,IJ20, IJ22, IJ28, simultaneously to actuator reducing efficiency IJ42,IJ43 move the ink. Each Multiple actuators actuator need provide can bepositioned to only a portion of the control ink flow force required.accurately Linear A linear spring is used Matches low travel Requiresprint head IJ15 Spring to transform a motion actuator with higher areafor the spring with small travel and travel requirements high force intoa Non-contact method longer travel, lower of motion force motion.transformation Coiled A bend actuator is Increases travel Generallyrestricted IJ17, IJ21, IJ34, actuator coiled to provide Reduces chiparea to planar IJ35 greater travel in a Planar implementations reducedchip area. implementations are due to extreme relatively easy tofabrication difficulty fabricate. in other orientations. Flexure A bendactuator has a Simple means of Care must be taken IJ10, IJ19, IJ33 bendsmall region near the increasing travel of not to exceed the actuatorfixture point, which a bend actuator elastic limit in the flexes muchmore flexure area readily than the Stress distribution is remainder ofthe very uneven actuator. The actuator Difficult to flexing iseffectively accurately model converted from an with finite element evencoiling to an analysis angular bend, resulting in greater travel of theactuator tip. Catch The actuator controls a Very low actuator ComplexIJ10 small catch. The catch energy construction either enables or Verysmall actuator Requires external disables movement of size force an inkpusher that is Unsuitable for controlled in a bulk pigmented inksmanner. Gears Gears can be used to Low force, low Moving parts are IJ13increase travel at the travel actuators can required expense ofduration. be used Several actuator Circular gears, rack Can befabricated cycles are required and pinion, ratchets, using standard Morecomplex drive and other gearing surface MEMS electronics methods can beused. processes Complex construction Friction, friction, and wear arepossible Buckle plate A buckle plate can be Very fast movement Must staywithin S. Hirata et al, “An used to change a slow achievable elasticlimits of the Ink-jet Head Using actuator into a fast materials for longDiaphragm motion. It can also device life Microactuator”, convert a highforce, High stresses Proc. IEEE MEMS, low travel actuator involved Feb.1996, pp 418-423. into a high travel, Generally high IJ18, IJ27 mediumforce motion. power requirement Tapered A tapered magnetic Linearizesthe Complex IJ14 magnetic pole can increase magnetic construction poletravel at the expense force/distance curve of force. Lever A lever andfulcrum is Matches low travel High stress around IJ32, IJ36, IJ37 usedto transform a actuator with higher the fulcrum motion with small travelrequirements travel and high force Fulcrum area has no into a motionwith linear movement, longer travel and and can be used for lower force.The lever a fluid seal can also reverse the direction of travel. RotaryThe actuator is High mechanical Complex IJ28 impeller connected to arotary advantage construction impeller. A small The ratio of force toUnsuitable for angular deflection of travel of the actuator pigmentedinks the actuator results in can be matched to a rotation of the thenozzle impeller vanes, which requirements by push the ink againstvarying the number stationary vanes and of impeller vanes out of thenozzle. Acoustic A refractive or No moving parts Large area required1993 Hadimioglu et lens diffractive (e.g. zone Only relevant for al, EUP550,192 plate) acoustic lens is acoustic ink jets 1993 Elrod et al, usedto concentrate EUP 572,220 sound waves. Sharp A sharp point is usedSimple construction Difficult to fabricate Tone-jet conductive toconcentrate an using standard VLSI point electrostatic field. processesfor a surface ejecting ink- jet Only relevant for electrostatic ink jetsACTUATOR MOTION Volume The volume of the Simple construction High energyis Hewlett-Packard expansion actuator changes, in the case of typicallyrequired to Thermal Ink jet pushing the ink in all thermal ink jetachieve volume Canon Bubblejet directions. expansion. This leads tothermal stress, cavitation, and kogation in thermal ink jetimplementations Linear, The actuator moves in Efficient coupling to Highfabrication IJ01, IJ02, IJ04, normal to a direction normal to ink dropsejected complexity may be IJ07, IJ11, IJ14 chip surface the print headsurface. normal to the required to achieve The nozzle is typicallysurface perpendicular in the line of motion movement. Parallel to Theactuator moves Suitable for planar Fabrication IJ12, IJ13, IJ15, chipsurface parallel to the print fabrication complexity IJ33, IJ34, IJ35,head surface. Drop Friction IJ36 ejection may still be Stiction normalto the surface. Membrane An actuator with a The effective area ofFabrication 1982 Howkins USP push high force but small the actuatorcomplexity 4,459,601 area is used to push a becomes the Actuator sizestiff membrane that is membrane area Difficulty of in contact with theink. integration in a VLSI process Rotary The actuator causes Rotarylevers may Device complexity IJ05, IJ08, IJ13, the rotation of some beused to increase May have friction at IJ28 element, such a grill ortravel a pivot point impeller Small chip area requirements Bend Theactuator bends A very small change Requires the 1970 Kyser et al whenenergized. This in dimensions can actuator to be made USP 3,946,398 maybe due to be converted to a from at least two 1973 Stemme USPdifferential thermal large motion. distinct layers, or to 3,747,120expansion, have a thermal IJ03, IJ09, IJ10, piezoelectric differenceacross the IJ19, IJ23, IJ24, expansion, actuator IJ25, IJ29, IJ30,magnetostriction, or IJ31, IJ33, IJ34, other form of relative IJ35dimensional change. Swivel The actuator swivels Allows operationInefficient coupling IJ06 around a central pivot. where the net linearto the ink motion This motion is suitable force on the paddle wherethere are is zero opposite forces Small chip area applied to oppositerequirements sides of the paddle, e.g. Lorenz force. Straighten Theactuator is Can be used with Requires careful IJ26, IJ32 normally bent,and shape memory balance of stresses straightens when alloys where theto ensure that the energized. austenic phase is quiescent bend is planaraccurate Double The actuator bends in One actuator can be Difficult tomake IJ36, IJ37, IJ38 bend one direction when used to power two thedrops ejected by one element is nozzles. both bend directions energized,and bends Reduced chip size. identical. the other way when Not sensitiveto A small efficiency another element is ambient temperature losscompared to energized. equivalent single bend actuators. ShearEnergizing the Can increase the Not readily 1985 Fishbeck USP actuatorcauses a shear effective travel of applicable to other 4,584,590 motionin the actuator piezoelectric actuator material. actuators mechanismsRadial constriction The actuator squeezes Relatively easy to High forcerequired 1970 Zoltan USP an ink reservoir, fabricate single Inefficient3,683,212 forcing ink from a nozzles from glass Difficult to integrateconstricted nozzle. tubing as with VLSI macroscopic processes structuresCoil/uncoil A coiled actuator Easy to fabricate as Difficult tofabricate IJ17, IJ21, IJ34, uncoils or coils more a planar VLSI fornon-planar IJ35 tightly. The motion of process devices the free end ofthe Small area required, Poor out-of-plane actuator ejects the ink.therefore low cost stiffness Bow The actuator bows (or Can increase theMaximum travel is IJ16, IJ18, IJ27 buckles) in the middle speed oftravel constrained when energized. Mechanically rigid High forcerequired Push-Pull Two actuators control The structure is Not readilysuitable IJ18 a shutter. One actuator pinned at both ends, for ink jetswhich pulls the shutter, and so has a high out-of- directly push the inkthe other pushes it. plane rigidity Curl A set of actuators curl Goodfluid flow to Design complexity IJ20, IJ42 inwards inwards to reduce thethe region behind volume of ink that the actuator they enclose.increases efficiency Curl A set of actuators curl Relatively simpleRelatively large IJ43 outwards outwards, pressurizing construction chiparea ink in a chamber surrounding the actuators, and expelling ink froma nozzle in the chamber. Iris Multiple vanes enclose High efficiencyHigh fabrication IJ22 a volume of ink. These Small chip area complexitysimultaneously rotate, Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates The actuator canbe Large area required 1993 Hadimioglu et vibration at a high frequency.physically distant for efficient al, EUP 550,192 from the ink operationat useful 1993 Elrod et al, frequencies EUP 572,220 Acoustic couplingand crosstalk Complex drive circuitry Poor control of drop volume andposition None In various ink jet No moving parts Various otherSilverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and doesnot move. required to related patent eliminate moving applications partsTone-jet NOZZLE REFILL METHOD Surface This is the normal way FabricationLow speed Thermal ink jet tension that ink jets are simplicity Surfacetension Piezoelectric ink jet refilled. After the Operational forcerelatively IJ01-IJ07, IJ10-IJ14, actuator is energized, simplicity smallcompared to IJ16, IJ20, IJ22-IJ45 it typically returns actuator forcerapidly to its normal Long refill time position. This rapid usuallydominates return sucks in air the total repetition through the nozzlerate opening. The ink surface tension at the nozzle then exerts a smallforce restoring the meniscus to a minimum area. This force refills thenozzle. Shuttered Ink to the nozzle High speed Requires common IJ08,IJ13, IJ15, oscillating chamber is provided at Low actuator ink pressureIJ17, IJ18, IJ19, ink pressure a pressure that energy, as the oscillatorIJ21 oscillates at twice the actuator need only May not be suitable dropejection open or close the for pigmented inks frequency. When a shutter,instead of drop is to be ejected, ejecting the ink drop the shutter isopened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asthe Requires two IJ09 actuator actuator has ejected a nozzle is activelyindependent drop a second (refill) refilled actuators per nozzleactuator is energized. The refill actuator pushes ink into the nozzlechamber. The refill actuator returns slowly, to prevent its return fromemptying the chamber again. Positive ink The ink is held a slight Highrefill rate, Surface spill must Silverbrook, EP pressure positivepressure. therefore a high be prevented 0771 658 A2 and After the inkdrop is drop repetition rate Highly hydrophobic related patent ejected,the nozzle is possible print head surfaces applications chamber fillsquickly are required Alternative for:, as surface tension and IJ01-IJ07,IJ10-IJ14, ink pressure both IJ16, IJ20, IJ22-IJ45 operate to refill thenozzle. METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Long inlet The inkinlet channel Design simplicity Restricts refill rate Thermal ink jetchannel to the nozzle chamber Operational May result in a Piezoelectricink jet is made long and simplicity relatively large chip IJ42, IJ43relatively narrow, Reduces crosstalk area relying on viscous Onlypartially drag to reduce inlet effective back-flow. Positive ink The inkis under a Drop selection and Requires a method Silverbrook, EP pressurepositive pressure, so separation forces (such as a nozzle 0771 658 A2and that in the quiescent can be reduced rim or effective related patentstate some of the ink Fast refill time hydrophobizing, or applicationsdrop already protrudes both) to prevent Possible operation from thenozzle. flooding of the of the following: This reduces the ejectionsurface of IJ01-IJ07, IJ09-IJ12, pressure in the nozzle the print head.IJ14, IJ16, chamber which is IJ20, IJ22, IJ23-IJ34, required to eject aIJ36-IJ41, certain volume of ink. IJ44 The reduction in chamber pressureresults in a reduction in ink pushed out through the inlet. Baffle Oneor more baffles The refill rate is not Design complexity HP Thermal InkJet are placed in the inlet as restricted as the May increase Tektronixink flow. When the long inlet method. fabrication piezoelectric ink jetactuator is energized, Reduces crosstalk complexity (e.g. the rapid inkTektronix hot melt movement creates Piezoelectric print eddies whichrestrict heads). the flow through the inlet. The slower refill processis unrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill rate IJ04, IJ12, IJ24, between the ink inlet advantage of ink Mayresult in IJ27, IJ29, IJ30 and the nozzle filtration complex chamber.The filter Ink filter may be construction has a multitude of fabricatedwith no small holes or slots, additional process restricting ink flow.steps The filter also removes particles which may block the nozzle.Small inlet The ink inlet channel Design simplicity Restricts refillrate IJ02, IJ37, IJ44 compared to the nozzle chamber May result in a tonozzle has a substantially relatively large chip smaller cross sectionarea than that of the nozzle, Only partially resulting in easier inkeffective egress out of the nozzle than out of the inlet. Inlet shutterA secondary actuator Increases speed of Requires separate IJ09 controlsthe position of the ink-jet print refill actuator and a shutter, closingoff head operation drive circuit the ink inlet when the main actuator isenergized. The inlet is The method avoids the Back-flow problem Requirescareful IJ01, IJ03, 1J05, located problem of inlet back- is eliminateddesign to minimize IJ06, IJ07, IJ10, behind the flow by arranging thethe negative IJ11, IJ14, IJ16, ink-pushing ink-pushing surface ofpressure behind the IJ22, IJ23, IJ25, surface the actuator betweenpaddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34, IJ35, nozzle.IJ36, IJ39, IJ40, IJ41 Part of the The actuator and a Significant Smallincrease in IJ07, IJ20, IJ26, actuator wall of the ink reductions inback- fabrication IJ38 moves to chamber are arranged flow can becomplexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to ink Silverbrook, EPactuator of ink jet, there is no problem is back-flow on 0771 658 A2 anddoes not expansion or eliminated actuation related patent result in inkmovement of an applications back-flow actuator which may Valve-jet causeink back-flow Tone-jet through the inlet. NOZZLE CLEARING METHOD NormalAll of the nozzles are No added May not be Most ink jet systems nozzlefiring fired periodically, complexity on the sufficient to IJ01, IJ02,IJ03, before the ink has a print head displace dried ink IJ04, IJ05,IJ06, chance to dry. When IJ07, IJ09, IJ10, not in use the nozzles IJ11,IJ12, IJ14, are sealed (capped) IJ16, IJ20, IJ22, against air. IJ23,IJ24, IJ25, The nozzle firing is IJ26, IJ27, IJ28, usually performedIJ29, IJ30, IJ31, during a special IJ32, IJ33, IJ34, clearing cycle,after IJ36, IJ37, IJ38, first moving the print IJ39, IJ40, IJ41, head toa cleaning IJ42, IJ43, IJ44,, station. IJ45 Extra In systems which heatCan be highly Requires higher Silverbrook, EP power to the ink, but donot boil effective if the drive voltage for 0771 658 A2 and ink heaterit under normal heater is adjacent to clearing related patentsituations, nozzle the nozzle May require larger applications clearingcan be drive transistors achieved by over- powering the heater andboiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used with: success-ion rapid succession. Inextra drive circuits depends IJ01, IJ02, IJ03, of actuator someconfigurations, on the print head substantially upon IJ04, IJ05, IJ06,pulses this may cause heat Can be readily the configuration of IJ07,IJ09, IJ10, build-up at the nozzle controlled and the ink jet nozzleIJ11, IJ14, IJ16, which boils the ink, initiated by digital IJ20, IJ22,IJ23, clearing the nozzle. In logic IJ24, IJ25, IJ27, other situations,it may IJ28, IJ29, IJ30, cause sufficient IJ31, IJ32, IJ33, vibrationsto dislodge IJ34, IJ36, IJ37, clogged nozzles. IJ38, IJ39, IJ40, IJ41,IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple solution Notsuitable where May be used with: power to not normally driven to whereapplicable there is a hard limit IJ03, IJ09, IJ16, ink pushing the limitof its motion, to actuator IJ20, IJ23, IJ24, actuator nozzle clearingmay be movement IJ25, IJ27, IJ29, assisted by providing IJ30, IJ31,IJ32, an enhanced drive IJ39, IJ40, IJ41, signal to the actuator. IJ42,IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle High IJ08,IJ13, IJ15, resonance applied to the ink clearing capabilityimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic blockages. This is actuators easiest toachieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear severely AccurateSilverbrook, EP clearing plate is pushed against clogged nozzlesmechanical 0771 658 A2 and plate the nozzles. The plate alignment isrelated patent has a post for every required applications nozzle. A postmoves Moving parts are through each nozzle, required displacing driedink. There is risk of damage to the nozzles Accurate fabrication isrequired Ink The pressure of the ink May be effective Requires pressureMay be used with pressure is temporarily where other pump or other allIJ series ink jets pulse increased so that ink methods cannot bepressure actuator streams from all of the used Expensive nozzles. Thismay be Wasteful of ink used in conjunction with actuator energizing.Print head A flexible ‘blade’ is Effective for planar Difficult to useif Many ink jet wiper wiped across the print print head surfaces printhead surface is systems head surface. The Low cost non-planar or veryblade is usually fragile fabricated from a Requires flexible polymer,e.g. mechanical parts rubber or synthetic Blade can wear out elastomer.in high volume print systems Separate A separate heater is Can beeffective Fabrication Can be used with ink boiling provided at thenozzle where other nozzle complexity many IJ series ink heater althoughthe normal clearing methods jets drop ejection cannot be used mechanismdoes not Can be implemented require it. The heaters at no additionalcost do not require in some ink jet individual drive configurationscircuits, as many nozzles can be cleared simultaneously, and no imagingis required. NOZZLE PLATE CONSTRUCTION Electroformed A nozzle plate isFabrication High temperatures Hewlett Packard nickel separatelyfabricated simplicity and pressures are Thermal Ink jet fromelectroformed required to bond nickel, and bonded to nozzle plate theprint head chip. Minimum thickness constraints Differential thermalexpansion Laser Individual nozzle No masks required Each hole must beCanon Bubblejet ablated or holes are ablated by an Can be quite fastindividually formed 1988 Sercel et al., drilled intense UV laser in aSome control over Special equipment SPIE, Vol. 998 polymer nozzle plate,which is nozzle profile is required Excimer Beam typically a polymerpossible Slow where there Applications, pp. such as polyimide orEquipment required are many thousands 76-83 polysulphone is relativelylow cost of nozzles per print 1993 Watanabe et head al., USP 5,208,604May produce thin burrs at exit holes Silicon A separate nozzle Highaccuracy is Two part K. Bean, IEEE micromachined plate is attainableconstruction Transactions on micromachined from High cost ElectronDevices, single crystal silicon, Requires precision Vol. ED-25, No. 10,and bonded to the alignment 1978, pp 1185-1195 print head wafer. Nozzlesmay be Xerox 1990 clogged by adhesive Hawkins et al., USP 4,899,181Glass Fine glass capillaries No expensive Very small nozzle 1970 ZoltanUSP capillaries are drawn from glass equipment required sizes aredifficult to 3,683,212 tubing. This method Simple to make form has beenused for single nozzles Not suited for mass making individual productionnozzles, but is difficult to use for bulk manufacturing of print headswith thousands of nozzles. Monolithic, The nozzle plate is High accuracy(<1 Requires sacrificial Silverbrook, EP surface deposited as a layerμm) layer under the 0771 658 A2 and micromachined using standard VLSIMonolithic nozzle plate to form related patent using VLSI depositiontechniques. Low cost the nozzle chamber applications lithographicNozzles are etched in Existing processes Surface may be IJ01, IJ02,IJ04, processes the nozzle plate using can be used fragile to the touchIJ11, IJ12, IJ17, VLSI lithography and IJ18, IJ20, IJ22, etching. IJ24,IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39,IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a Highaccuracy (<1 Requires long etch IJ03, IJ05, IJ06, etched buried etchstop in the μm) times IJ07, IJ08, IJ09, through wafer. Nozzle MonolithicRequires a support IJ10, IJ13, IJ14, substrate chambers are etched inLow cost wafer IJ15, IJ16, IJ19, the front of the wafer, No differentialIJ21, IJ23, IJ25, and the wafer is expansion IJ26 thinned from the backside. Nozzles are then etched in the etch stop layer. No nozzle Variousmethods have No nozzles to Difficult to control Ricoh 1995 Sekiya platebeen tried to eliminate become clogged drop position et al USP 5,412,413the nozzles entirely, to accurately 1993 Hadimioglu et prevent nozzleCrosstalk problems al EUP 550,192 clogging. These 1993 Elrod et alinclude thermal bubble EUP 572,220 mechanisms and acoustic lensmechanisms Trough Each drop ejector has Reduced Drop firing IJ35 atrough through manufacturing direction is sensitive which a paddlemoves. complexity to wicking. There is no nozzle Monolithic plate.Nozzle slit The elimination of No nozzles to Difficult to control 1989Saito et al instead of nozzle holes and become clogged drop position USP4,799,068 individual replacement by a slit accurately nozzlesencompassing many Crosstalk problems actuator positions reduces nozzleclogging, but increases crosstalk due to ink surface waves DROP EJECTIONDIRECTION Edge Ink flow is along the Simple construction Nozzles limitedto Canon Bubblejet (‘edge surface of the chip, No silicon etching edge1979 Endo et al GB shooter’) and ink drops are required High resolutionis patent 2,007,162 ejected from the chip Good heat sinking difficultXerox heater-in-pit edge. via substrate Fast color printing 1990 Hawkinset al Mechanically strong requires one print USP 4,899,181 Ease of chiphead per color Tone-jet handing Surface Ink flow is along the No bulksilicon Maximum ink flow Hewlett-Packard TIJ (‘roof surface of the chip,etching required is severely restricted 1982 Vaught et al shooter’) andink drops are Silicon can make an USP 4,490,728 ejected from the chipeffective heat sink IJ02, IJ11, IJ12, surface, normal to the Mechanicalstrength IJ20, IJ22 plane of the chip. Through Ink flow is through theHigh ink flow Requires bulk Silverbrook, EP chip, chip, and ink dropsare Suitable for silicon etching 0771 658 A2 and forward ejected fromthe front pagewidth print related patent (‘up surface of the chip. headsapplications shooter’) High nozzle packing IJ04, IJ17, IJ18, densitytherefore IJ24, IJ27-1145 low manufacturing cost Through Ink flow isthrough the High ink flow Requires wafer IJ01, IJ03, IJ05, chip, chip,and ink drops are Suitable for thinning IJ06, IJ07, IJ08, reverseejected from the rear pagewidth print Requires special IJ09, IJ10, IJ13,(‘down surface of the chip. heads handling during IJ14, IJ15, IJ16,shooter’) High nozzle packing manufacture IJ19, IJ21, IJ23, densitytherefore IJ25, IJ26 low manufacturing cost Through Ink flow is throughthe Suitable for Pagewidth print Epson Stylus actuator actuator, whichis not piezoelectric print heads require Tektronix hot melt fabricatedas part of heads several thousand piezoelectric ink jets the samesubstrate as connections to drive the drive transistors. circuits Cannotbe manufactured in standard CMOS fabs Complex assembly required INK TYPEAqueous, Water based ink which Environmentally Slow drying Most existingink dye typically contains: friendly Corrosive jets water, dye,surfactant, No odor Bleeds on paper All IJ series ink jets humectant,and May strikethrough Silverbrook, EP biocide. Cockles paper 0771 658 A2and Modern ink dyes have related patent high water-fastness,applications light fastness Aqueous, Water based ink whichEnvironmentally Slow drying IJ02, IJ04, IJ21, pigment typicallycontains: friendly Corrosive IJ26, IJ27, IJ30 water, pigment, No odorPigment may clog Silverbrook, EP surfactant, humectant, Reduced bleednozzles 0771 658 A2 and and biocide. Reduced wicking Pigment may clogrelated patent Pigments have an Reduced actuator applications advantagein reduced strikethrough mechanisms Piezoelectric ink- bleed, wickingand Cockles paper jets strikethrough. Thermal ink jets (with significantrestrictions) Methyl MEK is a highly Very fast drying Odorous All IJseries ink jets Ethyl volatile solvent used Prints on various FlammableKetone for industrial printing substrates such as (MEK) on difficultsurfaces metals and plastics such as aluminum cans. Alcohol Alcoholbased inks Fast drying Slight odor All IJ series ink jets (ethanol, 2-can be used where the Operates at sub- Flammable butanol, printer mustoperate at freezing and others) temperatures below temperatures thefreezing point of Reduced paper water. An example of cockle this isin-camera Low cost consumer photographic printing. Phase The ink issolid at No drying time-ink High viscosity Tektronix hot melt changeroom temperature, and instantly freezes on Printed ink typicallypiezoelectric ink jets (hot melt) is melted in the print the printmedium has a ‘waxy’ feel 1989 Nowak USP head before jetting. Almost anyprint Printed pages may 4,820,346 Hot melt inks are medium can be used‘block’ All IJ series ink jets usually wax based, No paper cockle Inktemperature with a melting point occurs may be above the around 80° C.After No wicking occurs curie point of jetting the ink freezes No bleedoccurs permanent magnets almost instantly upon No strikethrough Inkheaters consume contacting the print occurs power medium or a transferLong warm-up time roller. Oil Oil based inks are High solubility Highviscosity: this All IJ series ink jets extensively used in medium forsome is a significant offset printing. They dyes limitation for use inhave advantages in Does not cockle ink jets, which improved paperusually require a characteristics on Does not wick low viscosity. Somepaper (especially no through paper short chain and wicking or cockle).multi-branched oils Oil soluble dies and have a sufficiently pigmentsare required. low viscosity. Slow drying Microemulsion A microemulsionis a Stops ink bleed Viscosity higher All IJ series ink jets stable,self forming High dye solubility than water emulsion of oil, water,Water, oil, and Cost is slightly and surfactant. The amphiphilic solublehigher than water characteristic drop size dies can be used based ink isless than 100 nm, Can stabilize High surfactant and is determined bypigment concentration the preferred curvature suspensions required(around of the surfactant. 5%)

1. An ink jet printhead nozzle arrangement comprising: a wafer substratean ink chamber formed therein; an ink ejection port formed by asubstantially centrally located rim on a wall of said chamber; at leastone flexible portion located on said wall; and rib elements located onthe outer surface of said wall whereby the wall is adapted to moveindependently of said rim such that upon actuation the at least oneflexible portion displaces and interacting with the rib elements movessaid wall into said ink chamber forcing ink therein, out through thesaid ink ejection port; wherein the wall is configured to bend into theink chamber away from the centre of the ink chamber; and wherein thesaid at least one flexible portion of said wall is made from materialhaving a thermal expansion suitable to cause the wall to move into saidink chamber upon uneven heating of the at least one flexible portion ofthe wall.
 2. The arrangement according to claim 1, wherein at least aportion of the rib elements extend radially with respect to the inkejection port.
 3. The arrangement according to claim 1, wherein aheating element is located in conductive contact with each flexibleportion of the wall.
 4. The arrangement according to claim 3 whereineach heating element is serpentine in shape to allow for unhinderedexpansion of the flexible wall portion.
 5. The arrangement according toclaim 4 wherein each heating element is located remote from the rim ofthe ink ejector port.
 6. The arrangement according to claim 1 wherein anink inlet channel formed in said wafer substrate and is in communicationwith said ink chamber.
 7. The arrangement according to claim 6 whereinthe ink inlet channel enters into said ink chamber opposite the saidwall.